I played doctor with the girl across the street when I was 4. Her mom saw us (we didn't think to hide), and I was banned from the house. After that we played doctor in the trees, I honestly can't how long it went on. We progressed as far as touching, but it wasn't even remotely sexual, just curiosity. After that ... nothing.
That a get pity and shows, how narrow minded and ignorant her mum was. This is just what kids do, they are more inquisitive than many adults.
Kids are learning sponges. They soak up everything they see or hear. Remember how big your little world was when you were that age. Everything seemed enormous. But how small it has become when you grow older.
That is so true. Reaching up for door handles, climbing into the car or bed and the bath was a small swimming pool.